When a power supply device is initially activated to supply power voltages to a client device (e.g., a driver integrated circuit (IC)), excessive transient currents and latch-up effects occurring at the output of the power supply device may be susceptible to cause damage and failure of the client device. An excessive transient current, which may be caused by electrostatic discharge or circuit inner residual charges, may result in an excessive amount of heat and burn the internal circuitry of the power supply device, jeopardizing the system reliability. In addition, the latch-up effect, usually triggered by the input of an overload transient current or voltage to the client device, may disrupt the proper operation and possibly leading to the destruction of circuit components in the client device.
To remedy the aforementioned problems, FIG. 1 illustrates a conventional approach for preventing excessive transient currents and latch-up effects when the power supply device is initially activated. For this purpose, a protection circuit is externally coupled with each voltage output of a power supply device 102 where a client device is to be connected (not shown). Each protection circuit typically includes an Schottky diode coupled between one output of the power supply device 102 and a reference voltage. For example, with respect to a negative voltage output VN, a Schottky diode 104 is forward-connected from the output VN to a ground potential. For a positive voltage output VP, a Schottky diode 106 is forward-connected from another reference voltage VDD to the positive voltage output VP. While these external protection circuits provide effective shunting paths to release excessive transient currents, extra manufacturing costs are required.
Excessive transient currents and latch-up effects can also be prevented by providing a latch-up detection circuit, as disclosed in U.S. Pat. No. 7,221,027, the disclosure of which is incorporated herein by reference. However, the approach disclosed in this patent still requires a complex layout and additional semiconductor devices, which increases the manufacturing cost.
Therefore, there is a need for a system and method that can overcome the aforementioned issues in a more cost-effective manner.